The use of litter as a sorbent for pet animal urine and other waste liquids has been known for years. Typically, the litter is placed into a container or in an area which the pet has been trained to use for urinating and defecating. Many prior art litters have been derived from sand, clay, and other minimally sorbent materials. More recently the useful life and sorbency of these litters has been increased by addition of binders and other additives which cause a clump to form from litter soiled by urine and fecal liquids. See e.g., U.S. Pat. Nos. 5,216,980 and 5,176,107. Formation of soiled litter into a clump, in part, minimizes the spread of urine or fecal liquids thus minimizing contamination of the unsoiled litter surrounding the excreted waste liquids.
More recently, natural products such as grains, or cellulosic products such as sawdust, woodchips or plant hulls have been used as a litter. See e.g., U.S. Pat. Nos. 4,206,718; 4,727,824; 4,883,021; 5,109,804; 5,152,250. These products were developed in an effort to enhance the sorbency of the litter as well as provide a biodegradable litter which could be flushed down a commode attached to a septic or sewer system. However, although biodegradable, some natural product litters tend to swell excessively when contacted with aqueous liquids and thus cause problems such as blocking the sewer or septic lines when flushed down a commode.
In addition, after wetting, some prior art litters do not form a clump from the wetted (soiled) litter. The failure of soiled litter to form a clump makes it difficult to separate the soiled litter from the unsoiled litter, thus tending to cause greater contamination of the unsoiled litter. Therefore, analogous to the use of binders in minimally sorbent litters, some natural product litters have also relied on binders to cause formation of a clump. See e.g., U.S. Pat. No. 5,152,250. However, the clumps formed by some of these litters often have a high tendency to crumble after drying. A litter which forms a clump which crumbles easily tends to leave soiled litter particles in the unsoiled litter during removal of the clump from the litter container or by the weight of a pet stepping on the clump prior to removal. This obviously increases the chances for contamination of the unsoiled litter.
Moreover, the clumps formed by some prior art litters often have poor attrition resistance. Poor attrition resistance may cause contamination of the unsoiled litter by soiled particles which are abraded from the solid clumps during removal of the clump from the litter container. Also, certain litters, after being wetted and dried, may not reform into a clump if broken and rewetted. The repeated contamination of unsoiled litter by particles of soiled litter results in a decreased useful life of the litter.
Furthermore, the process used to prepare some natural product litters causes the litter to take on a noticeable odor which may be unpleasant for the pet owner. An odor emanating from the litter may also prevent an animal from voiding in the litter container resulting in urination or defecation at places other than the litter container. This obviously can create problems for a pet owner sharing the same living space as the pet.
Thus, there exists a need for an improved natural litter product which is biodegradable, low swelling, low odor and which when soiled tends to form a scoopable clump which is relatively attrition resistant and does not crumble easily after drying.